ABSTRACT The prevalence of low back pain (LBP) among U.S. adults is estimated at 20%, with 50-80% of people reporting a significant episode at some point in their life, and 23% of LBP patients reporting pain of high intensity with disability. The greatest burden placed on society occurs when LBP becomes chronic (cLBP). Inadequately managed chronic pain results in greater loss of productivity; increased expenditures for hospitalization, surgery and medications; and costly out-of-pocket patient expenses. Given their high rates of musculoskeletal disease, cLBP-related disability is rampant within our nation's Veteran population. The combination of cLBP and high medication use negatively impacts Veterans' work productivity and quality of life, and generates substantial risk for long-term disability and opioid addiction. There is arguably no more important population than Veterans for performing research to evaluate effective non-pharmacological treatments that are safe, pain relieving, cost-effective, and contain promise to restore function and quality of life. One such option is chiropractic care. Several key factors support the need to deepen the study of chiropractic care within the Veteran population: 1) biological models offer strong support for plausibility; 2) sufficient strength of evidence in systematic reviews has garnered a recommendation by American College of Physicians for spinal manipulation and/or chiropractic care targeting cLBP, and 3) since beginning in 2004, the Veterans Health Administration (VA) has successfully integrated 115 doctors of chiropractic into ambulatory care settings. These advances in chiropractic care integration have occurred despite substantial knowledge gaps, particularly within VA. Specifically, studies examining the delivery of chiropractic interventions have been highly variable and there is no optimal ?dosing? in terms of treatment duration or number of visits. Thus, the proposed study of Veterans age 18 and older with a diagnosis of cLBP is highly significant. Demonstration project investigators will work closely with the NIH-DOD-VA Collaboratory to accomplish the following project Aims: 1) Plan and develop the pragmatic research infrastructure needed to deliver a rigorous, multi-site, randomized controlled trial within the VA addressing 15 milestones in four categories of activities; 2) Evaluate the comparative effectiveness of a low dose (1-5 visits) of standard chiropractic care against a higher dose (8- 12 visits) in Veterans with cLBP; 3) Evaluate the comparative effectiveness of chiropractic chronic pain management (CCPM) compared to usual care, following the initial treatment described in Aim 1; 4) Evaluate the impact of CCPM on health services outcomes, compared to usual care; 5) Evaluate patient and clinician perceptions of non-specific treatment factors, effectiveness of study interventions, and impact of the varying doses of standard chiropractic care and the CCPM on clinical outcomes across 3 VA facilities using a mixed method, process evaluation approach.